Signaling system



March 19, 1946- H. n. M PHERSON SIGNALING SYSTEM Filed Dec. 20, 1944 V wM M m 1 ME W H A h NP EC ukuzuxtig V A v p Q W v vw I z t 0 uh an ,H HHE w Kw fix mw/L .?atented 29, N45 I estates stares parent opticsSKGNALHNG SYSTEM Hugh D. MacPherson, West New Brighton, N. Y, assignorto Roll il'elephorie Laboratories, Hncorporated, New York, N. Y, acorporation or New York Application December 20, mt, Serial No. ceases4Claims. on. 179-43) .signals from being displayed. at the stations whenattempts to initiate outward calls are made at both stationssimultaneously.

A feature of the invention resides in providing sources of bothpositiveand negative signal potentials at each station, arranging the circuitsso that one station transmits positive potenial to the line as anoutgoing or calling signal and negative potential when an incomingcallis answered at the inward terminal and the other station transmitsnegative polarity when initiating,

ward operator's positions and inward jack 2 at exchange B and inwardjack a at exchange A are likewise located at inward positions of theswitchit Of relay 5 t0 the mid-point H of the left-hand initiate a call,the respective difierential relay will be electropolarized in such adirection that it will be responsive only to signal potentialtransmitted from the distant station, which has the same polarity asthat of the transmitted calling or outgoing signal.

The invention will be understood from the following description whenread in connection with the accompanying drawing which shows a trunkline extending between two central oflices, or exchanges, A and B andarranged for two-way differential duplex signaling over a so-calledground composite circuit including one of the two conductors of the line(upper or tip conductor in the drawing).

A description of the operation of the system,

as shown by the drawing, will best serve to explain the feature of theinvention, and therefore it will be first assumed that an outwardoperator at exchange A, who has access to outward jack I of the line Ldesires to call the inward operator at exchange B, who has access to theinward or answering jack 2 at that exchange. As before mentioned it willbe understood that the inward jacks and associated signal devices ateach exchange are located apart from the respective outward jack, and wewill therefore assume that the outward jack 5 at exchange A and outwardjack 3 at exchange B are located at corresponding outboard at theseexchanges.

As it is to be assumed that an outward call is to be initiated atexchange A for exchange B, the outward operator at A will insert a plug5 of one of her cord circuits into jack l thus operating the sleeverelay 5 of the line, from battery over the sleeve of the plug 5 intheusual manner which circuit includes contact 8 of relay 3.

Qperation of relay t'performs two functions,

the first being to connect signaling current to the line, in the presentcase of positive polarity, which can be traced from positive battery t,and contact winding of difierential line relay l2 from which point itflows to the line through the right-hand portion of the winding and alsothrough the left portion to ground. The current applied to the lineflows over conductor it, winding of retardation coil M and upper or tipconductor of the line L, and passes to ground at station B over windingsof retardation coil l5, conductor l6, left=hand portion of theright-hand winding of line relay ii, contacts it of relay it, andcontacts 2!] of sleeve relay 2i. Current flowing from battery 9 hasdiilerential action on relay l2 due to the fact that current passes toground in opposite directions through the two halves of the relaywinding and consequently this relay is not energized thereby, but relayl i at station B is energized due to current flowing in only theleft-hand portion of its right winding, its right-hand portion beingshort circuited at. this time.

Relay ii at station B, in operating, lights the line signal (lamp 22) atthe inward position which circuit can be traced from ground, contacts ofrelay ll, contacts 23 of relay it and winding of relay 24 to battery,which relay operates to close its lowermost contacts to light lamp 22over the upper contacts of relay 2i. Relay 2% also opens its contacts 25thus preventing outward sleeve tacts 30 thereby completing an obviouscircuit to energize the polarizing winding 3| of differential line relayI2 in such a manner-that this relay thereafter, as long as relay 6 isoperated,

will only operate in case a positive potential is applied to the line atstation B to efiectively short-circuit its right-hand portion of thelefthand winding, which will be the condition when the inward operatorat station B inserts an answering plug 32 in the inward Jack 2 tooperate sleeve relay fl. The operation of this relay (2| opens itscontact 20 thereby removing ground from the mid-point 33 of theright-hand windaaeavsa ergize the polarizing winding of this relay andat station B relay i8 will energize the polarizing winding of relay 38or the respective differential relay i1- and connect negative potentialto the line at that end thereby causing current to flow fromthe-positive pole of battery 9 at station A to the negative pole or thebattery 43 at station B in series with the right-hand half of the leftto the flux caused by current, from battery 9, in

the left-hand portion of the winding aided by the flux caused by thepolarizing winding 3! winding of relay l2 and the left-half of therighthand winding of relay II. Under this condition signaling battery 9at station A and battery 43 at station B are in series with the linewhich will cause a flux in both relays i2. and i1 suflicient to overcomethe flux tending to operate these relays caused by the balancingportions of the relay windings plus the aiding polarizing flux andtherefore neither relay i2 nor i! will operate until one or the other orthe outward operators disconnects.

What is claimed is: v

1. In a telephone signaling system, a pair of stations, a linetherebetween, outward and inward line terminals at each station, asignal device associated with each inward terminal, duplex signaling.means including a differential relay at each station interconnected by asigwhich, as before mentioned, is in such a direction as to produce thiseffect. Relay 12 in operating causes relay to operate in a circuit fromground, contact of relay |2, contact 31 of relay'B, and winding of relay35 to battery, which latter relay, in closing its contacts places a lowresistance bridge. across the condenser in the switchboard side of therepeating coil 36 to ac' tuate a supervisory relay in the outwardoperators cord circuit (not shown) to cause a previously ,lightedsupervisory lamp to be extinguished as an indication to the operatorthat the called station hasanswered, which is well-known practice. Atthis .point it should be mentioned that relays l2 and ll, described, maybe of the type described in United States Patent 1,673,884

to H. c. Pye, issued June 19, 1928.

Operation in the other direction, i. c., for an outgoing call frOmstation E to station-A will be the same, that is insertion of an outwardoperators plug in jack 3 at station B will connect negative polarity atcontacts 38 of relay iii to the ,mid-point 33 of the winding of relay l1and also energize the polarizing winding 39'of that relay which willcause relay i2 at station A to operate, which in turn operates relay 8and lights line lamp 40 in the inward position associated with lack 4iand when the inward operator at station A answers, relay AI will operateto extinguish line lamp 40 and substitute negative potential for theground normally connected to the midpoint ii of the winding of relay I2.

When relay '8 operatesit opens its contact i ,thus preventingsubsequentattempts at the outward position to initiate outward callsfrom efiectingthe established circuit.

Connection of negative potential from the line at station A inopposition to corresponding potential connected at station E to holdrelay I2 operated and causing relay I! to operate due to its polarizingflux to energize winding 39 whereupon relay 32 is operated to extinguishthe outward operator's supervisory lamp.

'In case, however, that outward operators at both ends of the lineshould simultaneously seize outward jacks i and 3, relays 6 and I9 willoperate. Under this condition, relay Ii will connect positive polarityto the line by way of the midpoint ll of the winding of relay i2 andalso ennaling channel, each relay being normally operative to displaythe respective signal device when a' connection is established with thedistant end of the line by way of the outward terminal thereat,characterized in this that each of said relays is 'adapted to beelectropolarized in a predetermined manner, responsive to a connectionto the line by way of the respective 'outward terminal to preventoperation of said relay in-case a simultaneous connection is made withthe line by way of the outward terminal at the distant station.

2. In a duplex signaling system, a line, stations at each end thereof,positive and negative polarity sources of signaling potentials at eachstation, means at one station for connecting positive polarity to theline for initiating transmission of a signal thereover, and forconnecting negative-polarity when answering a signal transmitted fromthe distant station, and means at the second station for connectingnegative polarity to the line for initiating a signal over the line andfor connecting positive polarity to answer a signal transmitted from thefirst station, differential relay means in said line at each station soarranged that connection of a potential source at a station to initiatea call will actuate the differential relay at the called station andsubsequent connection of the same polarity to the line at the calledstation will hold the relay thereat 0perated and cause operation of therelay at the calling station, and means efiective when signal initiationpotential is connected to the line at a station to prevent therespective relay at that station from operating in case potential of theopposite polarity is simultaneously connected to the line at the otherstation.

3. In a duplex signaling system, a line, stations at each end thereof,positive and negative polarity sources of signaling potential at eachstation, means at one station for connecting positive p0 larity to theline for initiating transmission of a signal thereover and forconnecting negative pomitted from the first station, relay means in said4 line at each station so arranged that connection of a potential sourceat a station to initiate a call will actuate the diilerential relay atthe called station and subsequent connection of the same polarity totheline at the called station will hold the relay thereat operated andcause operation of the relay at the calling station, and means effectivewhen signal initiation potential is connected to the line at a stationto electrically bias the respective relay at that station in such adirection that the relay will not operate in case signal initiationpotential is simultaneously connected to the line at the other station.

4. In a duplex signaling system, a line, stations at each end thereof,outgoing and incoming line terminals at each station, signalingpotential at each station, a diflerential relay associated with of theline at one station causes operation of the relay at the other stationand subsequent connection of potential to the input terminal at saidother station holds the relay thereat operated and also causes the relayat said one station to operate, and means responsive to the simultaneousconnection of signaling potential to the outward terminal at bothstations for preventing either of said relaysfromoperating, said meanscomprising an electropol'arizing winding on each relay which isenergized in a predetermined direction responsive to connection ofsignaling potential to the outgoing line terminal at the correspondingstation.

HUGH D. MscPl-IERSON.

